The parents of a man who died after police used CS spray during an arrest have called for a swift and thorough investigation.

Gerard McMahon, from the Short Strand area of Belfast, was taken ill during the incident in Great Victoria Street in the city at about 5am on Thursday morning.

His mother and father, Gerard and Ella, said they wanted space to grieve.

"Our family are grieving for our son and brother Gerard and are calling on the Police Ombudsman's office to carry out a thorough and swift investigation into the circumstances of his death," they said.

"We would ask that the media would respect the privacy of our family at this sad time."

The Police Service of Northern Ireland initially said officers had responded to reports of a man behaving violently on the street and that he suffered injuries while being restrained.

The case was transferred to the Police Ombudsman's office which confirmed CS spray had been used.

The incident took place near the Grand Opera House and investigators are examining reports of an altercation between Mr McMahon and taxi drivers before the police arrived on scene.

A defibrillator was left on the street following the incident and Mr McMahon received medical attention before he was taken to hospital where he died.

Sinn Fein councillor Mairead O'Donnell visited the family and expressed her sympathy following Mr McMahon's death.

"The McMahon family are understandably devastated by the loss of their son at this very difficult time," she said.

Investigators from the ombudsman's office mapped and photographed the scene and security camera footage was recovered.

A number of witnesses have been spoken to but the office has issued an appeal for anyone else who was in the area at the time and may have seen what happened to contact them.

The Police Ombudsman renewed its appeal for 36-year-old Mr McMahon.

It urged anyone who saw him in Belfast city centre in the early hours of Thursday morning, particularly in the area of Great Victoria Street, to contact it.